Slow grain cooling is a proven, widely adopted and effective technique to cool grain that has been dried in a heated-air grain dryer. Steeping (short-term storage without aeration) and slowly cooling hot, dried grain will efficiently remove an additional one to four points of moisture. There are three recognized main advantages of slowly cooling grain that has been dried in a heated-air dryer: increased drying capacity, reduced operating costs for drying, and improved grain quality.
Specific known processes utilizing slow grain cooling include in-bin cooling, combination high-temperature/low temperature drying and dryeration. Of these processes, dryeration has the greatest potential for rapidly and efficiently reducing moisture content in grain.
In the dryeration process, hot, dried grain is discharged from a heated-air dryer into a grain bin, tank or other grain container where two separate grain conditioning sub-processes occur. The hot grain is first stored without aeration in a container at its removal temperature from the dryer for a predetermined period of time to permit the grain to steep. The removal temperature is the temperature the grain is discharged from the heated air grain dryer, typically 140.degree. F. to 160.degree. F. During this time, usually from four to twelve hours, temperature and moisture tend to become uniform within each kernel. Then the steeped grain is cooled by moving ambient air through it. This dryeration process (steeping and then cooling by aeration) has been commonly found to remove up to four additional points of moisture from the grain after the grain leaves the heated air grain dryer, in addition to the points of moisture removed in the dryer.
The amount of moisture removed in the grain steeping and cooling process is dependent upon the difference of the grain temperature entering and the grain temperature leaving the process and the time the grain is steeped. Although not well verified by research, considerable experience indicates adequately steeped grain will lose 0.20 to 0.25 percentage points of moisture for each 10.degree. F. temperature reduction. The temperature at which the grain leaves the dryer and enters the steeping process is dependent upon the drying air temperature and the efficiency of the heated air grain dryer. Common grain temperatures of grain leaving a dryer operating between 180.degree. F. and 200.degree. F. is 140.degree. F. to 160.degree. F., but both higher and lower dryer operating temperatures and therefore grain temperatures also do occur. The grain temperature will remain at this temperature during steeping and until the grain enters the cooling process, when it is cooled by aeration with ambient air. The temperature of the grain leaving the cooling process is a few degrees below the ambient air temperature. Although an ambient temperature range of 50.degree. F. to 60.degree. F. is common during the fall, both higher and lower temperatures are frequently encountered. Following are two examples of approximate low and high expected moisture reductions during the grain steeping and cooling process: EQU low, [(100.degree. F.-70.degree. F.)+10.degree. F.].times.0.20 points/10.degree. F.=0.60 points EQU high, [200.degree. F.-20.degree. F.)+10.degree. F.].times.0.25 points/10.degree. F.=4.50 points
One problem with the dryeration process as currently employed is that it is normally practiced as a batch process requiring two grain bins or tanks. Thus, a substantial capital investment is required.
Those concerned with these and other problems recognize the need for an improved slow grain steeping and cooling process.